I have taken my furnace out and reinstalled without removing the exhaust.? It does take a bit of reaching into the cabinet and wiggling to get it aligned.
I had an issue with bee nest inside the pipe.? I caught it before it got to the sail switch.? But I think bees may be a big problem with interfering with the movement.??
I wonder if you could use a leaf blower to blow into the exhaust so any debris at the intake would blow out the intake.? But look into both intake and exhaust first to clean anything you can see.
The circuit board makes sure the sail switch opens AND closes to prove it is freely moving before allowing gas.
I placed a screen over the outside to keep bees out.? The purchased screen comes with some springs to clip it on.? I smeared a thin coat of clear silicone over the top surface of the screen, back to the wall and just slightly over the edges to create a rain/drip cap.? I don't often use the furnace as a cube heater on low in more than enough and typically have electric.
